And now, we turn to the groundbreaking news here at home today. From Yale university, about American children and guns. Every hour, a child is rushed to the emergency room because of gunshots. And ABC's anchor, David Muir, is here on a story we've been working on together for nearly a year. David? That's right, Diane. The two of us teaming up and traveling across this country. And on the eve of our special report, "Young guns," later, the Numbers rorpted in the journal "Pediatrics." Looking at children and guns. Take a look. They are eye-opening. The new Numbers are arresting. One child or teenager every hour, injured by a firearm in this country. The study, tonight, revealing that 7,391 children rushed to the hospital every year with those gun injuries. So often, accidents in the home. 453 of those children die at the hospital. You've seen it often when it's an accident inside the home. Yes, I have. And it's devastating. Reporter: Dr. Robert latter of Lennox hospital of New York, has spent many years in the E.R. At one point, the doctor saying he was seeing gunshots in children twice a week. He says the new window into the E.R., into the horror seen with children and guns, he's been witnessing firsthand for some time. These are gunshot wounds that have happened inside the home, generally? They're a result of accidents where a gun safe is left unlocked. And teens and children gain access. Reporter: Tonight, the authors of the study calling this a national health problem. And for nearly a year, ABC news has traveled coast-to-coast, into neighborhoods where the Numbers tell us one in three homes in America have a gun. 1.7 million children live in a home with an unlocked and loaded firearm. And as part of our reporting, an experiment. We turn to the parents who say they've taught their children gun safety. Those parents agreed to take part at an elementary school in St. Petersburg, Florida. Seven hidden cameras. And for half the kids, reinforcing the message with a teacher. Who shows them the NRA Eddie eagle. Guiding them through the program. Don't touch. Leave the area. Tell an adult. Reporter: And the police come in with a gun safety class, repeating the message. And just listen to the children who have it down. Stop. Don't touch. Leave the area. Tell an adult. Reporter: Just a few days later, the police come in to place two real, unloaded guns inside the classroom. The teacher running the experiment, telling the children, they're there for a memory test. And she has to go for a second. But there's candy on the table. Among the pairs of children, William and griffin there, in their case, ten minutes after this. Don't mess with it. Reporter: There is this. One child looking down the barrel of the gun. I can't see. I told you. Reporter: His friend, about to do the same. I'm just seeing -- Reporter: Both of them, already having looked down the barrel by the time they call an Help? Help? Help? Help? Help? Anyone? We found a gun. Two guns. I mean, three. Two guns. Reporter: From a control room, the professor and the police watching. To look down the barrel. Reporter: And the parents who agreed to it all, looking, too. Friday night, you'll hear from the parents. The children watch the video with them. And, Diane, you begin the conversation Friday night about whether or not parents out there ever really ask the neighbors or their friends' parents if there's a gun in the home, whether it's lock, loaded or put away. We want to hear from everyone, joining forces on all sides of this issue. Thank you, David.

This transcript has been automatically generated and may not be 100% accurate.

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